1. Field of Invention
The present invention relates to the field of color imaging devices, and particularly to single-chip image and video camera.
2. Description of Related Art
Traditional cameras use film to store images. Analogously, a digital camera uses a solid state device called an image sensor to store images.
Image sensors are built on silicon chips containing millions of photosensitive diodes named photocells. Each photocell records the intensity of brightness of light shone on the photocell.
Moreover, each photocell reacts to light by accumulating a charge that directly corresponds to the brightness of the light. The brightness recorded is then converted to a set of numbers that can be used to digitally save the image and set the color and brightness of pixels on the screen or ink on printed page to reconstruct the image.
A Charge-Coupled Delay (CCD) sensor uses a non-standard semiconductor process to manufacture the photocell. Image-processing for a CCD sensor is normally done in a separate chip set.
A conventional design for the CCD digital camera includes an image sensor, an analog-to-digital converter (ADC) chip to convert sensory signal into digital form, a companion chip to handle image-processing and data/control input and output, and external memory interface for data storage element. Such designs requires tremendous amount of collaborative effort to establish communications between different chips, and therefore is non-optimal in terms of form factor and power consumption.
Due to a recent rapid growth of demand for the digital camera consumer market, an abundant supply of image sensors at a low per unit cost has become critical. Furthermore, it is crucial for image sensors to consume low power and be small in size in order to effectively construct digital cameras that are compact with a long battery life.
Accordingly, there is a need to produce cost effective image sensors that are small in size and consume low power.